ADHD children are at risk for a variety of negative outcomes as adolescents and young adults, including high school failure, delinquency, and substance abuse (Barkley et al, 2007; Lee et al, 2011; Molina et al, 2009; Sibley et al, 2011). Stimulant medication is the most widely used intervention for ADHD and has documented acute benefits for adolescents (Evans et al, 2000; Findling et al., 2011; Smith et al, 1998). However, long-term benefits have not been documented (Molina et al, 2009). By the end of adolescence, 80-90% of teens with ADHD are noncompliant with stimulant medication use, arguably the primary cause of the lack of long-term benefit (Biswas et al., 209; Molina et al, 2009). We propose to evaluate a dual component family-based intervention for adolescents with ADHD to improve medication adherence (Supporting Teen Adherence and Responsibility; STAR). STAR pairs Motivational Interviewing (MI; Miller and Rollnick, 2013) with parent-teen behavioral contracting (PTBC; Barkley, Edwards, Robin, 1999) to address the unique needs of ethnically diverse, primarily Hispanic, adolescents with ADHD. In the proposed study, 200 adolescents with ADHD and a history of chronic NA to their ADHD medication will be randomly assigned to medication alone (medication as usual: MAU) or MAU+STAR. As most ADHD youth are treated in primary care settings (Rushton, Kant & Clark, 2004), all participants will receive ADHD medication from their own primary care provider (PCC) for the duration of the study, and all visits will be held in the offices of their PCC. To test the intervention's acute and long-term efficacy, the study will examine treatment effects on adherence (MEMS cap pill count, monthly phone diaries) across six months of active intervention, one year of maintenance intervention, and a final year of naturalistic follow-up. In addition to monthly MEMS cap and phone diary assessments of adherence, participants' functioning will be assessed at intake, 6 months, 18 months, and 30 months in order to detect group differences in DBD symptomatology, academic functioning, family conflict, and substance use. The specific aims are to examine (1) the impact of STAR on medication adherence, (2) moderators of intervention effects on adherence, (3) if the intervention improves the functioning of adolescents with ADHD in four key domains: ADHD/ODD symptom severity, academics, family conflict, and substance use. Despite the alarmingly high rates of medication NA in ADHD, this proposal is the first randomized trial of an intervention specifically designed to improve medication adherence in adolescents with ADHD.